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Proper estimation of the thermal contact conductance at the stator-housing interface of electrical machines is necessary for the accurate prediction of thermal performance, since this material interface typically lies in the main heat extraction path. However, thermal contact conductance is a complex phenomena influenced by many factors including material properties, interface pressure and surface...
High performance electrical machine operation is limited by the losses generated in the machine and how well the heat developed by these losses is extracted. For conductive heat transfer from the main winding body, the insulation materials provide the main heat transfer pathway. As a machine ages through its lifetime, these materials will change their properties, and therefore these heat transfer...
This paper presents a method to predict and control current ripple in permanent magnet AC drives. First, analytical expressions for the switching-period current ripple are determined in the synchronous reference frame. These are then used to determine closed form expressions for fundamental-cycle averaged current ripple. The technique described is applicable to salient and non-salient pole permanent...
This paper presents an approach to the thermal design of an AC machine where the application requires a low-duty transient operation. To provide accurate temperature predictions the design process has been informed with experimental data from tests on a stator-winding sector (motorette). These have been shown to be a time and cost-effective means of calibrating the thermal model of a full machine...
The paper assesses the potential of employing super-junction MOSFETs in a high efficiency and low cost bidirectional DC-DC converter for application in electric vehicle systems. Super-junction MOSFETs have a very low conduction loss, however, their poor intrinsic diode recovery behaviour and high output capacitances means that switching losses can be high in voltage source converters. A drain current...
With the proliferation of electrical machines into functions previously undertaken by mechanical systems, the demand for compact, high energy and torque density, high performance electrical machines has increased. The thermal behaviour of an electrical machine and its degradation over time is a critical factor, particularly if high reliability is a requirement. A designer needs good knowledge of the...
The shrink-fitting of housings on to electrical machine stators is a common, semi-permanent and low-cost method of assembly. As the stator-housing interface lies in the main heat extraction path, an ideal shrink-fit should provide the necessary holding torque, present minimal thermal contact resistance and remain mechanically and thermally stable over the operating temperature range and life of the...
In this paper a performance comparison of permanent magnet (PM) salient rotor topologies is conducted. The analysis has been carried out for a machine design case study where numerous design requirements need to be satisfied simultaneously. The requirements include: low speed, high torque, low-duty transient operation and zero-speed injection based sensorless control capability. The majority of work...
In this paper a computationally efficient high-fidelity multi-physics design tool applicable to E-core power inductors is developed. The tool is composed of 2-D electromagnetic and 3-D thermal finite analyses coupled to models for inductor core and winding loss. The models are fully parametrically defined and appear as a black-box problem which can be used to perform parameter studies or design optimisation...
In this paper a design approach for a sensorless controlled, brushless, interior permanent magnet machine is attained. An initial study based on established electrical machine formulas provides the machine's basic geometrical sizing. The next design stage combines a particle swarm optimisation (PSO) search routine with a magneto-static finite element (FE) solver to provide a more in depth optimisation...
Cloud computing is a type of distributed computing that enables public, on-demand network (internet) access to a large pool of shared computing resources, making it easier than ever to outsource computing tasks on a pay-as-you-go basis. In this paper, a cloud computing service is used to complement an existing high-fidelity multi-physics power inductor design workflow by enabling multiple instances...
For a permanent magnet (PM) motor used in an electro-hydrostatic actuation system, fluid drag loss in the air gap can be as high as 60% of motor internal losses and affects the motor efficiency; especially at low temperatures where the viscosity of the hydraulic fluid increases significantly. A PM motor has been designed and built to assess electromagnetic, fluid drag loss and dynamic performance...
This paper reviews recent developments in power loss analysis applicable, but not limited to, the thermal design of electrical machines. Accurate and computationally efficient loss prediction is an essential element in thermal analysis of electrical machines, and has become an increasingly important part of the machine design-development process.
A methodology is proposed whereby performing a series of tests on a stator/winding subassembly can estimate the thermal envelope of a modular-wound single-layer machine topology. Concentrated windings offer many advantages, such as reduced manufacturing costs, improved thermal performance and readily lend themselves to fault-tolerant designs. Single-layer modular windings have inherent magnetic, thermal...
This paper presents an iterative coupled electromagnetic and thermal design methodology applied to a short-duty high-force-density permanent magnet tubular linear actuator. A difficulty with such coupled methodologies is balancing the accuracy of the modelling methods with the computation time. This problem is often addressed by employing a relatively detailed electromagnetic model and a coarse low...
This paper investigates the use of aluminium (Al) as an alternative to the more common copper (Cu) conductors used in the construction of future cost effective PM machines. The use of Al conductors in the context of PM machine design has not been widely explored or reported in the literature. The main focus of this research has been placed on the power loss generated at ac operation and associated...
The equivalent bulk thermal properties of electrical winding samples are measured experimentally. An analytical relation and a finite element thermal model of the conductor and insulation amalgam are compared with the test results. The thermal parameters are verified by the construction and dc test of three air-cored inductors with differing material configurations. The finite element implementation...
When designing high-bandwidth embedded linear actuation systems, engineers often face the choice between using a piezo-electric or electro-magnetic actuator. Often, actuator performance characteristics such as energy density, stiffness, frequency response and loss are used to specify the system configuration, whilst the power electronic drive requirement is overlooked. This paper demonstrates the...
Salient brushless AC (BLAC) permanent magnet (PM) motors are a preferred topology in the rapidly growing area of electric vehicle traction due to their inherent high efficiencies and excellent power densities. In the design of these systems it is important to appraise the motor performance across the entire torque-speed envelope. This paper presents computationally efficient techniques that allow...
A coupled electromagnetic-thermal design methodology is introduced and applied to the design of a short-duty, high-specific force linear actuator which serves to demonstrate the strong relationship between duty cycle, thermal performance and machine force density. It is shown that in the presence of a short well-defined duty cycle a machine can be designed to operate, transiently, well above its steady...
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